Sterling BB1230 B2B Charger Not Working

Hey folks,

I recently installed a Sterling Power BB1230 battery to battery charger in my Sprinter caravan and it doesn't seem to be working properly. For those who aren't familiar, it's supposed to use the alternator to charge my LiFePO4 house battery bank.

With the engine off:

- Starter battery voltage (SBV) is 12.65 V (so, fully charged)
- House battery voltage (HBV) is 13.15 V
- HBV current draw is 0.0 amps because I switched everything off (solar charger and 12V loads). This is according to a Victron battery monitor

When the engine is on and idling, the BB1230 automatically turns on, and I get:

- SBV is 14.1 (so, the 90 amp alternator is working)
- BB1230 input voltage is 13.8
- BB1230 output voltage is 13.5
- HBV current draw goes from 0 to NEGATIVE ~1 amp. Then it stays like that indefinitely (20 minutes is the longest I've checked). This is according to a Victron battery monitor

What's really strange is that if I disconnect the output wire to the house batteries, the measured input voltage immediately goes to 14V and the output goes to 14.4V. I thought, maybe, that there's a poor connection on the output side through the fuse and busbar, etc., so I bypassed all of it by wiring the output of the BB1230 directly to the batteries, but I got the same results as shown above.

The attached annotated graphics tell the story a little better:

This one shows how the BB1230 is wired.




This is a picture of the charger when it turns on. As soon as I disconnect the positive output wire to the battery, the input/output lights turn green at 14.2 V




This is house battery data from the Victron battery monitor during a test, different from the one that generated the voltages stated above. There's a small blip in current which indicates the engine start. Then, a short while later, the BB1230 turns on and the voltage increases to 13.3, but the current drops down to -1.1 amps. It does this every time and has never shown a different behavior since it was installed about a week ago.

Then, just to show that the battery monitor is working properly, I decided to switch on the 45 amp shore power charger, and the voltage and current increased to 13.5 V and +37.5 amps, which is exactly what it should do. I was expecting a similar response from the BB1230, except something less than +30 amps.



I'm using the battery monitor because I don't have an ammeter that's rated for 30 amps. This shows how the shore power charger is wired to the shunt/battery monitor. It's wired exactly the same way as the BB1230, so the monitor data should be reliable.




I've also measured resistances between various points and they've all been less than 500 milliohms. This includes between the battery and chassis ground.

Today, I installed a new 150 amp alternator and got the same results.

I've spoke with Adam (Sterling Power USA rep) and Jr. (UK Office), but they haven't been able to figure it out.

This might be an unrelated anomaly, but my 1500W inverter gives an alarm whenever the house bank reaches 100% SOC AND the solar charge controller (SCC) is charging. If I disable the SCC, the alarm turns off, and if I turn the SCC back, the alarm activates again. I replaced the SCC with a completely different make/model AND replaced the inverter with a new one and it still occurs. This makes me think something is wrong with my system, but I've checked everything I can think of and haven't found anything. Maybe this datapoint is a clue for the BB1230 issue I'm having?

Any ideas on what the culprit might be? Anyone know where I can borrow an ammeter rated for 30 amps? Would appreciate any help!!


Thanks!
Warren

Oh, and here's a peek at the inside build :

I don't see a wiring *diagram*, but if i'm reading the photos correctly (and the words in the image)
Do your house batteries have a separate wire to chassis ground directly from the house battery negative post??
(first photo, text in lower right corner pointing at yellow wire)
If so, it's bypassing the shunt. Which will confuse things.

The house battery should have ONE wire attached to its negative post, and that should ONLY go to the shunt.
The other end of the shunt should be treated as if it were the battery's negative ... so THAT's where the connection to the chassis should happen.
Your "redundant" wire to the starter battery negative could serve that purpose.

--dick

A couple of things to try:

1) Given the odd issue with your inverter alarm, I would remove everything (solar charger, inverter, shunt, etc..) and test the BB1230 output with nothing attached to the out side except the house batteries.
2) Sterling recomends connecting the BB1230 negative directly to the starter battery. My house battery is bonded to the chassis at the same bolt as the starter battery ground. So there's no direct connection betwen the house negative and the Sterling negative. You could test that by removing the negatives for the BB1230 and the start battery from the bus bar and clamping them together.
3) Is the ground bus bar bonded to the chassis?
4) It looks like a second positive (red) wire is leaving the positive buss bar. Where does that go? Has it been disconnected for testing?

If a basic wiring setup per the Sterling manual doesn't produce the correct charging then you must have a defective unit.

Is that a temp sensor on the house battery? I read somewhere that you shouldn't use the temp sensor for lithium charging with the BB1230, but I'm not sure if that came from Sterling or LifeBlue and I can't seem to find the reference again.

Good luck!

You aren't by chance running any DC loads of significance off the house battery bank are you? My fridge draws 15 amps DC when it is on battery. Make sure the Sterling settings are set up for lithium and you have the ignition sense wire properly connected.

autostaretx said:

I don't see a wiring *diagram*, but if i'm reading the photos correctly (and the words in the image)
Do your house batteries have a separate wire to chassis ground directly from the house battery negative post??
(first photo, text in lower right corner pointing at yellow wire)
If so, it's bypassing the shunt. Which will confuse things.

The house battery should have ONE wire attached to its negative post, and that should ONLY go to the shunt.
The other end of the shunt should be treated as if it were the battery's negative ... so THAT's where the connection to the chassis should happen.
Your "redundant" wire to the starter battery negative could serve that purpose.

--dick

Click to expand...

Ahh, makes sense. Thanks for the catch. I'll remove the ground from the battery to the chassis and run it from the shunt.

The BB1230 manual says the "redundant" wire from the starter battery negative is highly recommended to ensure common ground. I didn't think it was super necessary but they really insisted on it when I spoke with them.

-Warren

alborg said:

A couple of things to try:

1) Given the odd issue with your inverter alarm, I would remove everything (solar charger, inverter, shunt, etc..) and test the BB1230 output with nothing attached to the out side except the house batteries.

Click to expand...

Yup, tried this and got the same result.

alborg said:

3) Is the ground bus bar bonded to the chassis?

Click to expand...

Yes, but at the chassis near the starter battery. The system is also grounded to the chassis at the negative battery terminal.

alborg said:

4) It looks like a second positive (red) wire is leaving the positive buss bar. Where does that go? Has it been disconnected for testing?

Click to expand...

That's the output from the shore power charger.

alborg said:

If a basic wiring setup per the Sterling manual doesn't produce the correct charging then you must have a defective unit.

Click to expand...

That was my thought as well. I'm hoping that Sterling will send a replacement to try out, but something tells me it isn't defective. I mostly say that because of the inverter issue, and replacing it didn't work either.

alborg said:

Is that a temp sensor on the house battery? I read somewhere that you shouldn't use the temp sensor for lithium charging with the BB1230, but I'm not sure if that came from Sterling or LifeBlue and I can't seem to find the reference again.

Click to expand...

Interesting...I missed that when I went through the manual. I'll take another look!

-Warren

hoosierrun said:

You aren't by chance running any DC loads of significance off the house battery bank are you? My fridge draws 15 amps DC when it is on battery. Make sure the Sterling settings are set up for lithium and you have the ignition sense wire properly connected.

Click to expand...

I disabled all the DC loads and yes, the charger is configured for lithium. I'm in the default config so don't have the ignition wire installed.

As mentioned, if you have grounds bypassing the shunt, the monitor will not show the charging current. It sounds like the BB is seeing a full battery, so its going straight to float mode.

Midwestdrifter said:

As mentioned, if you have grounds bypassing the shunt, the monitor will not show the charging current. It sounds like the BB is seeing a full battery, so its going straight to float mode.

Click to expand...

Makes sense; however, the monitor shows charging current when the shore power charger and solar charge controller are charging, and the currents are what I would expect them to be. The BB is wired to shunt in the same way, but for some reason, it shows a negative current (-1 amp) when it powers on. I'm thinking this is its quiescent power that's required to run the fan, lights, etc.). I also don't think the BB uses the monitor to determine battery state of charge, but if it did and went straight to float mode, I'd expect the output voltage to be 14.4V and not 13.5V.

Perhaps I should draw up a wiring diagram -- I know the pictures are low-light and hard to see.

-Warren

OP needs to provide a detailed schematic including noting wire gauge and wire lengths. It's likely a wiring error.

The measured voltages indicate the B2B is functional. He measures 14.0V at the chassis battery and 13.8V at the B2B (hopefully both meter probes are at the correct locations). In other words, there's a 0.2V cable drop. A sizable current is flowing into the B2B!

On a side note, my guess the OP has a voltage measurement error. A 0.2V cable drop is way too big. Looks like 1/0 cable (0.1mohm/ft) between chassis battery and B2B. At 20 feet round trip, that's 2 mohm cable resistance.

Current = Cable drop / cable resistance = 0.2 V / 2 mohm = 100 A

We know there's no 100A. That means the voltmeter measurements are not accurate.

wdavi014 said:

Makes sense; however, the monitor shows charging current when the shore power charger and solar charge controller are charging, and the currents are what I would expect them to be. The BB is wired to shunt in the same way, but for some reason, it shows a negative current (-1 amp) when it powers on. I'm thinking this is its quiescent power that's required to run the fan, lights, etc.). I also don't think the BB uses the monitor to determine battery state of charge, but if it did and went straight to float mode, I'd expect the output voltage to be 14.4V and not 13.5V.

Perhaps I should draw up a wiring diagram -- I know the pictures are low-light and hard to see.

-Warren

Click to expand...

The alternator and BB charger use the chassis ground for negative return. the other items get there ground/negative from your bus bar, so they will be visible to the monitor.

calbiker said:

OP needs to provide a detailed schematic including noting wire gauge and wire lengths. It's likely a wiring error.

The measured voltages indicate the B2B is functional. He measures 14.0V at the chassis battery and 13.8V at the B2B (hopefully both meter probes are at the correct locations). In other words, there's a 0.2V cable drop. A sizable current is flowing into the B2B!

On a side note, my guess the OP has a voltage measurement error. A 0.2V cable drop is way too big. Looks like 1/0 cable (0.1mohm/ft) between chassis battery and B2B. At 20 feet round trip, that's 2 mohm cable resistance.

Current = Cable drop / cable resistance = 0.2 V / 2 mohm = 100 A

We know there's no 100A. That means the voltmeter measurements are not accurate.

Click to expand...

Working on a diagram now. The wire is mostly 6 AWG; that's the stuff running into the B2B from the starter battery which is 9ish feet away. Therefore, 8 mohm which yields 25 amps (expected). There's a short section of 1/0 from the pos busbar to the bank, and the heaviest stuff in the picture is 2/0 (overkill, but it's what I had on hand).

I agree -- I think it's a wiring issue, but I can't find it! I'm no electrician, but perhaps y'all can help me flush out a theory. The output should be close to 25 A, but I'm measuring -1 A (let's assume for a moment that the shunt is working properly, which I don't think is too far of a stretch cause it seems to work for the other chargers). So, could it be possible that there's a 26 A current loss due to an increase in resistance??

V=IR, so if V increases (slightly by 0.2 V), I decreases by 26 A, R would have to increase, right?

If there is a wiring issue, what's a good way to isolate it? Do i just measure resistance at different points?

Thanks everyone for all the input so far! I REALLY appreciate it!

We'll find the problem. Just need an accurate diagram.

We calculate resistance, and measure voltage.

The most accurate way to measure B2B input current is to measure the cable voltage drop. Place the + meter probe directly on the positive chassis battery terminal. Place the - meter probe on the positive input terminal of the B2B. Your probe leads won't be long enough as this distance is 9 ft. You're going to need a longer probe lead. Measure voltage drop (will be less than 0.2V) with alt operational.

Current = Voltage drop / (9 ft * 0.4 mohm/ft) = V_drop / 3.9 mohm

The wiring issue is with your current measurement and shunt wiring.

wdavi014 said:

If there is a wiring issue, what's a good way to isolate it? Do i just measure resistance at different points?

Click to expand...

The easiest way to find out what is happening is with a DC clamp meter.

Just as an example, something like an extech clamp meter with a low current range is what I use for things like that. There are other options, that is just what I have.

The smaller clamp makes it easy to get into tight locations.

Really anyone who has a van electrical system should probably own one, even before they buy a battery soc monitor.

Midwestdrifter said:

The alternator and BB charger use the chassis ground for negative return. the other items get there ground/negative from your bus bar, so they will be visible to the monitor.

Click to expand...

Hmm, I don't quite follow, but that's probably due to my lack of electrical knowledge. The B2B negative is connected to the bus bar. The bus bar is connected to the grounded house bank AND the starter battery chassis ground. So doesn't that mean they share a common ground?

Its hard to tell from your photo. On a shunt, NOTHING except the battery is connected to one side. All other connections are made to the load side (not battery side) of the shunt.

Here's the wiring schematic -- hope it doesn't suck too bad. I excluded fuses, breakers, and other stuff that isn't relevant.



Edit: I also didn't include wire gauge or lengths. I can tell you it's all over-sized and nothing smaller than 6 AWG.

Midwestdrifter said:

Its hard to tell from your photo. On a shunt, NOTHING except the battery is connected to one side. All other connections are made to the load side (not battery side) of the shunt.

Click to expand...

Yup, will definitely correct that -- probably this evening.

wdavi014 said:

Yup, will definitely correct that -- probably this evening.

Click to expand...

Why is the house bank grounded to the chassis, and before the shunt?









.

You probably now know what's wrong. The house battery has a direct connect to chassis ground. You have 2 ground paths from starter battery to house battery. You have the 6 gauge ground cable and the chassis ground to Li battery cable.

It turns out that the chassis ground cable has much lower resistance and as a result current is bypassing the shunt.

I would keep the chassis ground cable. Remove it from the Li battery and connect this cable to the negative bus bar. You can remove the cable from starter bat neg to bus bar neg. I would then install this (removed cable) and double up on the positive cable from starter battery. 6 awg really isn't big enough. Double up and you'll be better.