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Did I damage my AGM battery with a low 'float' voltage?

mkeys

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We have a 1 year old Sprinter cargo van that we use as a campervan. About 4-5 months ago I installed a charger that keeps the vans starter battery charged using energy from our 'house' battery/solar in the back of the campervan.

This charger comes on whenever the engine is off. It is a victron DC-DC charger, and I programmed it to supply 12.7v to the starter battery.

My goal with this charger was to keep the starter battery from getting into the 12.5/12.6v range where it starts to show warnings in the dashboard about a low battery. We sometimes use the vans built-in wifi router when the engine is off, which has a large draw, so without this charger we could run the battery down too much.

Recently I started to get an error in the dashboard of the van while driving warning that the battery was too low (suggesting I pull over and leave the engine running to charge it up).

It is an awfully new battery to be having issues, so I am thinking something about how I've been charging/maintaining this battery while the engine is off is killing it. I don't know enough about AGM chemistry/best practices to know what though.

I'd appreciate any help/insight from the community!
 
I had the battery tested today at an auto parts store and they verified that the battery is bad/needs to be replaced. I have to think that something I've done must have killed this battery as it is so new. I am hoping someone here can educate me as to how?
 
I mean. You do need to float lead batteries.

You should not have disabled float in my opinion.
 
I am thinking something about how I've been charging/maintaining this battery while the engine is off is killing it.
I agree with Short_Shot. Set your float to 12.6v.

I would also wire your loads so that no loads pull from the starter battery unless the engine is running. Don't use the built-in WiFi router (or anything else) that runs off the starter battery. Add another one that runs off the house batteries. The starting battery is for starting, that's your whole issue.
 
Depending on local regulations its possible the van has 'smart' alternator charging with start stop on the engine. There may be issues applying charge 'outside' the vans system control of battery charging.

The settings you have will not do much in the way of charging with an absorption voltage of 12.7 and a time of 1 m and float disabled.

If the intention is to charge the engine battery ( and its allowed by the vans system, see drivers handbook) then the absorption voltage should be around 14.6 volts with a float of 13.7 volts, time limit 5 hours with adaptive absorption 'on'.

A continuous maintaining charge voltage would be lower at around 13.2 volts

Using a Victron Orion to maintain the engine battery with power from the service battery is unusual, there are numerous low cost units available that carry out this maintaining task.

There are possible issues if there is a engine charging system in place for the service battery that is voltage level activated when the engine is started. If this is the case then an 'enable' single derived from 'key on' must be used so this system cannot be activated when the engine is stopped.
 
The standard absorption for an agm is 14.4 - 14.6v. Then it drops to float, which for long term is usually 13.2 - 13.4v for long term.

Your victron app shows that you have set it up improperly by disabling float altogether, and using too low of an absorb voltage. Your battery slowly sulfated from lack of a good charge. And so will your replacement if you don't correct your absorb (14.4v) and float (13.4v). And ENABLE it, unlike what your app shows. :)

I don't know where people get the idea that 12.8v is a good float voltage. It is NOT. Even cheap AGM battery maintainers typically follow the 14.4v absorb and 13.2v float at the least.
 
The app says float is disabled. The absorption s/b set at closer to 14.4 and the float at 13.4 volts. One hour absorption is probably too short... consider turning on the Adaptive function.

However does the DC-DC charger shut down overnight when the house battery is no longer charging?

What is the settings of the house battery solar controller?
 
Thank you for the feedback everyone.

The intention wasn't really to charge the starter battery, so much as put a 'floor' on how much it can discharge. My thought was that at a voltage of 12.7v, if the starter was higher than that there would be no current flowing from the house to the starter. Clearly that isn't exactly what happened as I've ended up with this bad battery.

In light of everything that has happened, I think I will keep this DC-DC charger off most of the time, and see if there is a stock profile for an AGM battery from victron that I can enable for when it is on.

I do use the vans wifi and cellular connection when on road trips so that I can work remotely. I have 2 years of unlimited data on that plan at a very reasonable price, around $20/mo if I recall, so it would be nice to still be able to use that if I can find a way to do it safely.

One thought might be to only turn on this charger when I am using the vans wifi. Another thought would be to only turn it on if I get a low voltage from the starter battery.

Some answers to questions/thoughts above:

Using a Victron Orion to maintain the engine battery with power from the service battery is unusual, there are numerous low cost units available that carry out this maintaining task.
Do you mean like battery maintainer units? I typically see these run from an AC source to plug into your garage or whatever. This solution is meant to be mobile and powered by the house batteries (700AH of LiFePO4)

Your victron app shows that you have set it up improperly by disabling float altogether, and using too low of an absorb voltage. Your battery slowly sulfated from lack of a good charge. And so will your replacement if you don't correct your absorb (14.4v) and float (13.4v). And ENABLE it, unlike what your app shows. :)
The thought, once again perhaps from a gross misunderstanding of how this works, was that the victron DC-DC would be setting a 'floor' of how low the starter can discharge. And when the engine was on, the alternator would be providing the battery its full 'good charge'

There are possible issues if there is a engine charging system in place for the service battery that is voltage level activated when the engine is started. If this is the case then an 'enable' single derived from 'key on' must be used so this system cannot be activated when the engine is stopped.
The house battery charges from the starter only when the engine is on. No voltage activation, there is a signal wire run from a terminal under the drivers seat back to the victron DC-DC charger. Well technically it runs to a relay that activates one of the two DC-DC chargers depending on engine state. This was done to ensure only one of the two chargers can ever connect to that starter battery at a time.

However does the DC-DC charger shut down overnight when the house battery is no longer charging?

What is the settings of the house battery solar controller?
It has been manually disabled since I started having issues. But when it was enabled, it was on so long as the engine was off. There is a lot of house battery to pull from and the max current from the DC-DC charger to the house was about 7A as it was configured, so there was no concern of 'running out'.

The house battery solar controller is a renogy MPPT 40A which charges the house LiFePO4 batteries (also renogy) using its own LiFePO4 charging profile.
 
Yes by disabling float and absorption set at one hour.... you are going to maintain 12.7 for one hour only. This will do little to nothing.

Set the DC-DC properly and use as needed.
 
Lead batteries need to be recharged pretty much at all times.

Letting it stay low like that is a no-no.

The victron sound just have a lead acid mode you can just turn on and ignore.
 
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