Welcome to RVForums.com

  • Register now and join the discussion
  • Friendliest RV Community on the web
  • Modern site for PC's, Phones, Tablets - no 3rd party apps required
  • Ask questions, help others, review campgrounds
  • Get the most out of the RV Lifestyle
  • Invite everyone to RVForums.com and let's have fun
  • Commercial/Vendors welcome

Engine Battery Charge

Welcome to RVForums.com

  • Register now and join the discussion
  • Modern secure site, no 3rd party apps required
  • Invite your friends and let's have fun
  • Commercial/Vendors welcome
  • Friendliest RV community on the web

Ivan Yurtin

RVF Newbee
Joined
Mar 28, 2023
Messages
1
When I hook up to shore power with my Wayfarer, does the engine battery get charged as well as the coach battery?
Thanks,

Ivan Yurtin
 
Not like! Charging dissimilar batteries is a no no
 
Not like! Charging dissimilar batteries is a no no
The engine alternator charges my house batteries. It stands to reason that the house power could charge the chassis battery, I know it doesn't on mine but I could see how one might think it should.

Dissimilar batteries doesn't seem to be the key factor though. More an issue of how it's all wired together?
 
It seems every RV is different, even with a single manufacturer there are differences between models, years and it seems day to day in mfg.

We recently added a maintenance charger to our chassis battery, tied into a shore power circuit, so I didn’t have to be concerned or closely monitor the chassis batteries which power our HWH system, electric door locks and a couple other items I am forgetting at the moment.
 
When I hook up to shore power with my Wayfarer, does the engine battery get charged as well as the coach battery?
Thanks,

Ivan Yurtin
Well with no more information all I can say is It should. Best practise would be to test it and see. With it hooked up and the house batterys charged cheack the voltage on the Chassie batterys. They should be around 13.5-14.4 volts. if they are charging. 12.7 volts is full charged.
Bill
 
I almost turned this into a rant, but I tried to stop myself.

You could ask an engineer working in the battery industry for his opinion concerning connecting dissimilar batteries together, but I saved you the trouble.

In my opinion, the fact that how the RV industry acts like a bunch of backwoods shade tree mechanics on this topic, only serves to bring to light the true nature of the industry.

Now I can only tell you how this job should be done, but you have the right to do what you will. My history in electronics, industrial electrician, electric boats, tells me the two systems should not be connected unless temporarily for emergency purposes.

There is a reason I don't copy the industry's slipshaud practices.
It is a great way to build in problems.

Sorry for the rant, I tried not to, really I did.
 
Kevin,

I need to learn more about electrical, appears it will be a life long endeavor.

The OP asked if shore power would charge both chassis and house batteries.

If the batteries are not directly connected together nor charged from the same charger, would there be any harm in that?

In our coach the Outback Power System inverters/chargers are charging house batteries (2 lithium that are 450ah each) and we recently installed a separate “battery maintainer” to charge chassis batteries (3 lead acid commercial truck batteries). This battery maintainer is plugged into a circuit that is only powered by shore power.

Besides the L-BIM and emergency button for start assist, there is no connection between the two battery systems.

In your training and experience, would this configuration cause any issues?
 
Last edited:
I almost turned this into a rant, but I tried to stop myself.

You could ask an engineer working in the battery industry for his opinion concerning connecting dissimilar batteries together, but I saved you the trouble.

In my opinion, the fact that how the RV industry acts like a bunch of backwoods shade tree mechanics on this topic, only serves to bring to light the true nature of the industry.

Now I can only tell you how this job should be done, but you have the right to do what you will. My history in electronics, industrial electrician, electric boats, tells me the two systems should not be connected unless temporarily for emergency purposes.

There is a reason I don't copy the industry's slipshaud practices.
It is a great way to build in problems.

Sorry for the rant, I tried not to, really I did.

I'm not sure where you get dissimilar batteries from the OP's post. The default seems to be flooded cell lead acid batteries, at least that's what I have in my chassis and coach. OP didn't say they were running lithium or AGM in the coach. It may be non optimal charging deep cycle and starter batteries in parallel, and perhaps more so *if* either were deeply discharged However nothing in the original post indicated either situation.

Would it be better to have quality (and properly sized/configured) DC-DC and AC-DC dedicated chargers in place where cross system charging is happening? Certainly. However, that wasn't the OP's questions.
 
I will try to answer both statements and questions now.
A house bank and a starting battery of the same build, ie lead acid, agm, lithium, doesn't matter. If the battery has different age, size, or other dissimilar attributes, they charge and discharge differently. In the end game, they don't charge equally, heck they don't discharge any better.

Attempts have been made to fix this common problem. Likely you are familiar with this scheme, it is called equalizer mode, no? Listen carefully concerning lithium! This situation is not left to you the user. The reason lithium batteries require cc supplies is the corrective circuitry is in the BMS. The more expensive system work with active components, the lesser BMS has a balancing system using passive components like resistors to balance all the cells. As well as cut off circuitry to protect the cells from overcharging or low voltage. Never fully charging a lithium battery leads to unbalanced cell, as it is required for the balancing circuitry to do it's job!(talking possible fires here)

Lithium is less likely to have problems sharing the same charger!!! Because of the BMS. The reason a BMS is needed with lithium is lack of proper balancing is attributed to many device fires. Power walls skimp on the BMS! yes they are cheap, but they come with a fire risk. You can read into this part of the discussion what you want!

Bottom line is this! Dissimilar batteries can mean ANY difference between them, even age! With lithium we talk fires, with lead technology, we talk about the best battery self distructing, while the less capable battery plays catch up. I look at professionals that knowingly offer their customers products that have not been produced to offer best service criminal! There is to much information on batteries to consider this issue anything but neglect.
 

Latest resources

Back
Top