Sprinter-Forum    
 

Go Back   Sprinter-Forum > Sprinter-Based RV's & Conversions > Sprinter RV's & Conversions Talk

Sprinter RV's & Conversions Talk Common features found in Sprinter RV's and Conversions.


 
Thread Tools Display Modes
Old 01-14-2020, 08:16 PM   #1
russinthecascades
 
Join Date: May 2017
Posts: 79
Thanks: 34
Thanked 20 Times in 15 Posts
Default Shore charging questions

With the snow and overcast conditions recently in the PNW, I've needed to connect to shore power to recharge the system after consecutive 3 day/2 night out ski trips. Summer and fall were recovered/maintained quickly by the 400W solar alone. The accessible power at home is a 15A service, which is typically taking about 36 hours to go from 80% to 100% SOC. Current draw is from several LCD lights, 2 fans, recharging 2 phones and Espar D2 running most of the time.

System:
4x100 Ah Windy Nation AGM batteries
Victron 712 Battery monitoring system
Victron Multiplus 12/3000 Inverter/charger
12AWG connecting wire between shore inlet and inverter

Questions:
1. Does it matter (other than the time it takes) whether you shore charge from 15A, 20A or 30A service for the health of the batteries? Multiplus manual lists AC input current limits from 3A - 50A. Also states "for maximum battery life, a charge current of 10% - 20% of the capacity in Ah should be applied. Example: optimal current of a 24V/500Ah battery bank: 50A to 100A".
My equivalent would be 12V/400Ah: ?A to ?A (I'm not sure of the formula used to calculate the 10-20% amp range).

2. When charging from 15A service does the length of the extension cord or gauge of the wire play much of a role? I've used both 25' 14/3 and 100' 10/3. Thought about getting a 25' 10/3 if it helps.
russinthecascades is offline   Reply With Quote
Old 01-14-2020, 08:21 PM   #2
OrioN
2008 2500 170" EXT
 
OrioN's Avatar
 
Join Date: Sep 2007
Location: Vancouver, BC
Posts: 10,873
Thanks: 614
Thanked 2,712 Times in 1,981 Posts
Default Re: Shore charging questions

You need to refer to battery's manual for the correct charging spec's and guideline first or foremost.
OrioN is offline   Reply With Quote
The Following User Says Thank You to OrioN For This Useful Post:
russinthecascades (01-14-2020)
Old 01-14-2020, 09:02 PM   #3
calbiker
 
Join Date: Aug 2008
Location: Santa Barbara
Posts: 2,747
Thanks: 537
Thanked 1,270 Times in 827 Posts
Default Re: Shore charging questions

The charger outputs 120A.
Output power = 120A * 14.4V = 1728 W

Input power = Output power / efficiency
Input power = 1728W /0.8 = 2160 W
Input current = 2160W / 120V = 18A

That means 15A service is too low. You need 20A.

The length of ac cable and gauge plays a roll.
14 awg = 2.5 mOhm/ft
10 awg = 1.0 mOhm/ft

Line drop for 14 awg, 25 ft = 50 ft * 18A * 2.5 mOhm/ft = 2.25V
Line drop for 10 awg, 100 ft = 200 ft * 18A * 1 mOhm/ft = 3.6V

That means if you use 25 ft length, 14 awg cable the voltage at the converter is 120V - 2.25V = 117.7V

The converter will need to work harder the larger the line drop. The batteries are not affected.

4 * 100AH = 400AH
Applied current = 120A/400AH = 30%

There's no problem charging at 30%
calbiker is offline   Reply With Quote
The Following User Says Thank You to calbiker For This Useful Post:
russinthecascades (01-15-2020)
Old 01-14-2020, 09:49 PM   #4
russinthecascades
 
Join Date: May 2017
Posts: 79
Thanks: 34
Thanked 20 Times in 15 Posts
Default Re: Shore charging questions

Quote:
Originally Posted by OrioN View Post
You need to refer to battery's manual for the correct charging spec's and guideline first or foremost.
Battery manual states:
Max Charge Current: 30 amps

Charge mode @ 77 degrees F (it's probably been around 35F in the van while charging)

Bulk 14.4V
Abs. 14.1 - 14.7V
Float 13.5V

I haven't been monitoring as it went through the charging stages, but did note this morning when it displayed 100% SOC it was 13.2V. What other battery information is needed?
russinthecascades is offline   Reply With Quote
The Following User Says Thank You to russinthecascades For This Useful Post:
OrioN (01-14-2020)
Old 01-14-2020, 10:49 PM   #5
HarryN
 
Join Date: May 2010
Location: Pleasanton, CA
Posts: 2,576
Thanks: 617
Thanked 830 Times in 676 Posts
Default Re: Shore charging questions

Something doesn't sound quite right.

Going from 80-100% should take 3-4 hrs, not 30-40 hrs.

One place to look is to see if the temp compensation is working.

If the charger thinks that it is just doing finishing state charging, and there are significant loads, perhaps that is slowing it down.

My van has a similar pack, 400 amp hrs of lifeline s wired 48 volt x 100 amp-hrs. The charger I am using is less powerful but could easily go from 50% SOC to completely full in 4-6 hrs.

Obviously lifeline s are different than windy nation but that is way too long.
__________________
Power systems for conversion vans and emergency preparedness.

https://wirlnet-inc.square.site
HarryN is offline   Reply With Quote
Old 01-14-2020, 11:10 PM   #6
john61ct
 
Join Date: Apr 2018
Posts: 1,713
Thanks: 29
Thanked 405 Times in 344 Posts
Default Re: Shore charging questions

Quote:
Originally Posted by russinthecascades View Post
Does it matter (other than the time it takes) whether you shore charge from 15A, 20A or 30A service for the health of the batteries? Multiplus manual lists AC input current limits from 3A - 50A. Also states "for maximum battery life, a charge current of 10% - 20% of the capacity in Ah should be applied.
Quality AGM can accept a **much** higher current rate.

For many makes, 0.2C would be the **minimum** rate for good longevity.

For some 0.4C, and again that's a minimum, even 0.6-0.8C will do no harm, lead in general is self-limiting and vendor "max current" specs a legal CYA fiction.

In short go for it,

get a 50A 240V circuit installed

just don't go high nor over long; keep voltage at the vendor's to Absorb spec, and stop charge at their endAmps spec.

Ideally, adapt your charger to accept J1772 input from EVSEs out on the road, just don't hog them when genuine EVs are queuing up or they could start blocking us.

Last edited by john61ct; 01-15-2020 at 12:47 AM.
john61ct is online now   Reply With Quote
Old 01-15-2020, 12:20 AM   #7
Shawn182
 
Join Date: Aug 2017
Posts: 289
Thanks: 7
Thanked 123 Times in 92 Posts
Default Re: Shore charging questions

Quote:
Originally Posted by john61ct View Post
get a 50A 240V circuit installed
His rig only has 12awg from shore power plug to inverter/charger. That would limit him to 20A max unless he also wants to learn how wires overeat and start fires.
Shawn182 is offline   Reply With Quote
Old 01-15-2020, 12:27 AM   #8
Sinorm
 
Join Date: May 2018
Location: Seattle, WA
Posts: 32
Thanks: 2
Thanked 18 Times in 12 Posts
Default Re: Shore charging questions

The problem isn't the shore power you are connecting to, something is wrong with the charging settings. Check to make sure you have the correct charge rate and voltages set for your batteries. As calbiker pointed out your 15A/120V service may or may not be able to charge at the maximum supported 120 amp rate, but it can certainly get close. You should be able to charge your batteries from completely empty to full in a few hours.
Sinorm is offline   Reply With Quote
The Following User Says Thank You to Sinorm For This Useful Post:
HarryN (01-15-2020)
Old 01-15-2020, 12:46 AM   #9
john61ct
 
Join Date: Apr 2018
Posts: 1,713
Thanks: 29
Thanked 405 Times in 344 Posts
Default Re: Shore charging questions

Quote:
Originally Posted by Shawn182 View Post
His rig only has 12awg from shore power plug to inverter/charger. That would limit him to 20A max unless he also wants to learn how wires overeat and start fires.
Yes obviously the infrastructure from start to finish needs to support 20% more than the maximum current it will ever see.

Did not think that needed stating, sorry. And thanks!

PS no extension cords when you get to very high currents. Since you need a pro to put in that 240 circuit, do your bits first and get them to inspect your whole setup while they're there.

Not officially take any responsibility of course, unless they want to charge over say an hour labor extra.

Last edited by john61ct; 01-15-2020 at 12:50 AM.
john61ct is online now   Reply With Quote
Old 01-15-2020, 12:52 AM   #10
Shawn182
 
Join Date: Aug 2017
Posts: 289
Thanks: 7
Thanked 123 Times in 92 Posts
Default Re: Shore charging questions

Also you said charing in the PNW after ski trip...what is the temp of the batteries when attempting charging? LiFepo4 systems and cold temps no workie.
Shawn182 is offline   Reply With Quote
The Following User Says Thank You to Shawn182 For This Useful Post:
SkyGypsy (01-17-2020)

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT. The time now is 04:22 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2020, vBulletin Solutions, Inc.