I need HELP!!!: Charging question

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Charging question

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Forum Name: I need HELP!!!
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Topic: Charging question

Posted By: Aboopoo
Subject: Charging question
Date Posted: 20 Jan 2021 at 11:49pm

I recently purchased two new 6 V batteries and the seller told me they should be charged for three days to get them right to the top with a 6volt 10 amp charger. If I plug my rpod 172 in and install the batteries, can you tell me what the amperage is, that the charger in the roped puts out.my meter shows 13.6volts. I would like to know this so that I could charge the batteries through my Rpod charger and not a separate charger on the bench.

Replies:

Posted By: offgrid
Date Posted: 21 Jan 2021 at 1:24am

At 13.6V your batteries are already more or less fully charged. The rpod charger can produce up to 55A but it will never do so for long, the charge rate will taper down quickly as the batteries charge. A 10 amp workbench charger’s current will taper down as well.

I think what your battery seller was saying is that you should leave the battery on the charger initially for 3 days minimum. That’s fine, it will ensure the electrolyte is fully mixed and all the battery cells are fully charged and equalized. It does not imply that the charger will be providing 10 amps (or 55 amps) that whole time. Your battery system capacity is going to be around 200 amp hours. 10 amps for 3 days is 720 amp hours, which would cook them.

So yes you can use your on board charger to charge your new batteries, and leaving it on for at least 3 days is good. In fact you can leave it on indefinitely. Just be sure to check the electrolyte level every few weeks and add distilled water as needed. Alternatively, you can disconnect the batteries (either by removing the wire from the negative terminal or by adding a battery disconnect at the positive terminal) after charging them, then reconnect and charge them for 2 or 3 days roughly once a month, checking the electrolyte level at the same time. You don’t want to leave the batteries connected without a charging source because the trailer parasitic loads will discharge them in a few weeks.

If you want to know for yourself how much current is going in or out of your batteries, charging sources, and load devices, get a clamp on multimeter that measures dc current. Those used to be expensive but are getting pretty cheap now. Be sure it measures dc current as well as ac, the technology used is different. Very handy tool for troubleshooting and managing battery use especially if you plan to boon dock much.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: jato
Date Posted: 21 Jan 2021 at 7:13am

+1 Another alternative which many chargers have is the 'trickle charge' mode. It charges at 2 amps. Do you have that option? Even if you do you need to follow offgrids advice on watching your electrolyte levels. Even at 2 amps the electrolyte will eventually cook and evaporate, albeit at a much slower rate.

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God's pod
'11 model 177
'17 Ford F-150 4WD 3.5 Ecoboost
Jim and Diane by beautiful Torch Lake
"...and you will know the Truth and the Truth will set you free."

Posted By: offgrid
Date Posted: 21 Jan 2021 at 8:48am

Any decent quality modern charger should shift from its bulk charge mode (which is limited by its max current output) over to absorption mode which is voltage limited. For the Wfco charger in your rpod that is 13.6 v. Then eventually it will go into float mode which is also voltage limited but at a slightly lower voltage (13.2 for the wfco) which maintains battery charge without consuming too much water. Some chargers have 4 stages. The point is that once the charger goes into a voltage limited mode it really doesn’t matter what it’s max current output is because it’s not controlling it’s charge rate based on current any more, it’s using battery voltage to control its output instead. The max current output only matters which it’s in bulk charge mode, which happens when the battery has been discharged significantly and doesn’t last very long.

Hope that makes sense.

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: Aboopoo
Date Posted: 21 Jan 2021 at 1:07pm

Thank you all for this information as it’s been very helpful to understand what the charge rates are and the amperage that the trailer charger can put out. As my trailer is stored at a facility that has no power I have to run I generator once a month or book a campsite close by for a couple of days to plug into 120 V. I was considering a solar panel but found that up in British Columbia during the winter months we can have quite a number of dark days and the MPPT charge controller becomes parasitic and bleeds some of the power down.

I have since installed a battery disconnect on the positive wire and completely any sources that could drain the battery. These are new batteries so I want to protect them and keep them fully charged best I can. I wasn’t sure if it made sense to pull the batteries out of the box and keep them on a bench for a month or two over the winter or leave them in and go out and charged with a portable generator from time to time. Given that the trailer put out good amperage I will use that instead of a portable charger on my generator. Thank you all for the good information and fast replies!

Posted By: jato
Date Posted: 21 Jan 2021 at 1:28pm

An alternative, which yours truly has done for the last 10 winters (northern Michigan) is to pull them out and set on a concrete floor in an unheated garage. After getting washed with baking soda and rinsed and then electrolyte levels checked they are given a 2 amp trickle charge for 24 - 36 hours in November and then 'hibernate' throughout the winter until the following end of April/first of May when the charge process is repeated before re-installing. Batteries are 10 and 9.8 years old and hold up very well to our boondocking camp style.

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God's pod
'11 model 177
'17 Ford F-150 4WD 3.5 Ecoboost
Jim and Diane by beautiful Torch Lake
"...and you will know the Truth and the Truth will set you free."

Posted By: offgrid
Date Posted: 21 Jan 2021 at 3:58pm

I agree with jato. In your case, poor solar access and no ac power at your storage facility, it will probably be easiest for you to bring your batts back to your home for the winter and maintain them there.

I wouldn’t assume that one charge will get you through the winter though. Your climate is not as cold as MI (cold reduces battery self discharge) and deep cycle 6V batteries will self discharge faster than 12v automotive type batteries (different battery plate chemistry) so I would either leave them on a good quality bench battery charger or charge them every few weeks until you get a feeling for what they need. The risk is that without adequate charging the battery electrolyte can stratify (acid migrates to the bottom of the cells, water to the top, and the battery plates can in turn form a sulfate layer which degrades their capacity. There really Is no downside to more aggressively charge them as long as you keep the plates covered by maintaining electrolyte levels (adding distilled water only).

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold

Posted By: jato
Date Posted: 21 Jan 2021 at 5:57pm

+1 I didn't pay attention to the fact that the OP has 6 volt batteries, hence the chemistry for charging/discharging is quite different.

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God's pod
'11 model 177
'17 Ford F-150 4WD 3.5 Ecoboost
Jim and Diane by beautiful Torch Lake
"...and you will know the Truth and the Truth will set you free."

Posted By: StephenH
Date Posted: 21 Jan 2021 at 7:35pm

No, the 6V batteries are the same lead-acid chemistry as the 12V batteries. The only times it would make a difference is if:

A. The batteries were AGM

B. The batteries were Gel

C. The batteries were LiFePO4.

The converter can handle flooded lead-acid batteries just fine, whether it is one 12V battery or two 6V batteries wired in series.

I believe that the converter can handle AGM batteries. I'm not sure about gel. I know the stock converter is not suitable for LiFePO4 batteries. I know because I installed an LiFePO4 battery and ended up removing the stock converter and installing the WF-8950L2 MBA, which is made for LiFePO4 batteries. I also ended up installing a DC to DC charger so my Frontier would properly charge the LiFePO4 battery while on the road.

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StephenH
Happy is the man that findeth wisdom,...

http://www.rpod-owners.com/forum_posts.asp?TID=7712 - ouR escaPOD mods
Former RPod 179
Current Cherokee Grey Wolf 24 JS

Posted By: offgrid
Date Posted: 21 Jan 2021 at 8:22pm

Originally posted by StephenH

No, the 6V batteries are the same lead-acid chemistry as the 12V batteries. The only times it would make a difference is if:

A. The batteries were AGM

B. The batteries were Gel

C. The batteries were LiFePO4.

The converter can handle flooded lead-acid batteries just fine, whether it is one 12V battery or two 6V batteries wired in series.

While all flooded lead acid batteries are the same basic chemistry there are definitely subtle differences in chemistry between batteries designed for various applications. Doesn’t generally change the charger setpoints, but it does impact the battery’s ability to handle differences in usage. In particular, battery plates are not generally pure lead, either calcium or antimony alloys are typically used to strengthen them. That creates differences in the ability of the batteries to handle deep cycling, and differences in their self discharge rates and water consumption. Like everything in life, there are trade offs. Read this:

https://www.engineersedge.com/battery/antimony_calcium_selenium_tin_alloying.htm

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1994 Chinook Concourse
1995 RV6A Experimental Aircraft
2015 Rpod 179 - sold