Renogy LiPo sudden discharged

[Bat21]

I fitted a 100ah Renogy Lithium battery to my Land Cruiser camper a few months ago, all has been good since fitting it.

As it is unlikely to be used over the winter I was going to put the battery into storage mode via the on/off switch that plugs into the RJ45 port. I was going to do this once the battery had discharged down to about 60%.

I have been checking the battery level every couple of days and 2/3 days ago it was 67%, this was after standing for about 3/4 weeks.
I checked it today and it was down to 6%, so it has lost about 60 of its charge in just 2-3 days.

Anyone else experienced this, is this a normal discharge pattern?

 

[Admin]

Is it a heated battery, and has the nighttime temperature near you dropped below 5 degrees?

 

[Bat21]

Is it a heated battery, and has the nighttime temperature near you dropped below 5 degrees?

Ah yes, you have a point there, yes it probably has for the last couple of nights.

Looks like I wrongly assumed that the battery heating only kicks in if it senses a charge input, which there wasn't.

I have pulled it out of its garage and today's cloudy sun juice has topped it up to 17% so I have now turned the battery off and parked it back up.

I must admit, I didn't expect it to pull 60% charge out of the battery with such a small heating element.

 

[Admin]

Ah yes, you have a point there, yes it probably has for the last couple of nights.

Looks like I wrongly assumed that the battery heating only kicks in if it senses a charge input, which there wasn't.

I have pulled it out of its garage and today's cloudy sun juice has topped it up to 17% so I have now turned the battery off and parked it back up.

I must admit, I didn't expect it to pull 60% charge out of the battery with such a small heating element.

It depends on how the battery calculates the remaining capacity; this calculation is likely based on battery voltage. This means that if some solar charge were going into the battery, it would raise the voltage and give an incorrect reading.

 

[wildebus]

Ah yes, you have a point there, yes it probably has for the last couple of nights.

Looks like I wrongly assumed that the battery heating only kicks in if it senses a charge input, which there wasn't.

I have pulled it out of its garage and today's cloudy sun juice has topped it up to 17% so I have now turned the battery off and parked it back up.

I must admit, I didn't expect it to pull 60% charge out of the battery with such a small heating element.

I guess some batteries algorithms may vary, but I was certainly under the impression that the heating element would only ever be activated by incoming power.

This is a PTC Heating Flowchart I was sent from a Manufacturer showing the process for one of their 100Ah Lithium Batteries.

PTC-Heating by David, on Flickr
(A PTC Heating Element are the most common type of heating for the LiFePO4 batteries with built-in heaters)

 

[Admin]

I guess some batteries algorithms may vary, but I was certainly under the impression that the heating element would only ever be activated by incoming power.

This is a PTC Heating Flowchart I was sent from a Manufacturer showing the process for one of their 100Ah Lithium Batteries.

PTC-Heating by David, on Flickr
(A PTC Heating Element are the most common type of heating for the LiFePO4 batteries with built-in heaters)

Earlier batteries from some brands without a bi-directional BMS and heating would use the batteries on power.

 

[Bat21]

Earlier batteries from some brands without a bi-directional BMS and heating would use the batteries on power.

I bought this Renogy one just before you told me about the Fogstar ones at the Stratford show..... if I'd have known before I would have gone down the Fogstar route with a single 300ah one.

 

[wildebus]

Earlier batteries from some brands without a bi-directional BMS and heating would use the batteries on power.

Interesting.
That would also mean that with that type of battery, if you had an external Battery SOC Monitor, such as a Victron BMV (or any brand), the SOC reading in cold weather (cold enough for the heater to come on), the reading would in fact be worthless.
(This is also true to a point for those batteries with the heaters that come on only with charge, but to a lesser degree).

This also raises an extra point for anyone who adds their own heating pad to a Lithium Battery and has an external monitor .... the -ve connection to that heating pad must be external to the battery and on the load side of the Monitors shunt, not the battery side.

 

[Admin]

Interesting.
That would also mean that with that type of battery, if you had an external Battery SOC Monitor, such as a Victron BMV (or any brand), the SOC reading in cold weather (cold enough for the heater to come on), the reading would in fact be worthless.
(This is also true to a point for those batteries with the heaters that come on only with charge, but to a lesser degree).

This also raises an extra point for anyone who adds their own heating pad to a Lithium Battery and has an external monitor .... the -ve connection to that heating pad must be external to the battery and on the load side of the Monitors shunt, not the battery side.

It was common for whole shipments of batteries to arrive in the UK flat as the heaters had been active in transit.

 

[Fisherman]

Yet I have had two Polarmax Explorer 100AH Lithium batteries with heaters in my garage for almost two years and they have lost very little charge.
Strange.

 

[Bat21]

Yet I have had two Polarmax Explorer 100AH Lithium batteries with heaters in my garage for almost two years and they have lost very little charge.
Strange.

Strange indeed.
I get why they would need to bring themself up to 5-10C when they sense a charge but not when they are pretty much doing nothing.

 

[Bat21]

It was common for whole shipments of batteries to arrive in the UK flat as the heaters had been active in transit.

The Fogstar ones don't appear to be able to be switched off so would they essentially flatten themselves in the winter months if the vehicle isn't used?

 

[wildebus]

The Fogstar ones don't appear to be able to be switched off so would they essentially flatten themselves in the winter months if the vehicle isn't used?

I am not familiar with the App used for the BMS, but definately not any setting to turn the heater on and off? (could be a weird description for the heater? some kind of 'chinglish' term?)

 

[rugbyken]

It was common for whole shipments of batteries to arrive in the UK flat as the heaters had been active in transit.

when we fitted my new battery it was completely flat which worried me at first as fogstar said they ship & store at 30-50% capacity but i had left it sitting on the garage floor for six weeks so the above has reassured me, also fogstar customer services were very quick to respond & explain the cell balancing sequence

 

[Bat21]

I am not familiar with the App used for the BMS, but definately not any setting to turn the heater on and off? (could be a weird description for the heater? some kind of 'chinglish' term?)

No not turn the heater off, I mean turn the whole battery off.
The Renogy ones come with a small switch that plugs in the battery comms port, this enables the battery to go into shelf/storage mode.
I gave up with Renogy support last night after waiting for almost an hour.

 

[Bat21]

For anyone who is following this, I have just come across this piece of info.
This suggests the heater should not have activated in the colder weather we had last month.

Looks like it's going to be later next week before it drops to 5 again so will keep an eye on it around then.

 

[Okta]

When low temperature Li batteries were first introduced they made a point of the heating elements only ever being powered by the incoming charge. The stored charge should not be used. Even if the heating elements are only switched on when there is incoming power there is still a potential for flattening the battery if the incoming charge is less than the heating elements use. A few milliamperes of winter solar or short bursts of sunlight will not be enough to replace the charge used by the elements. Far better to do the job properly and use the incoming charge, if it is not enough to warm the battery sufficiently nothing is lost from the stored power. It is the obvious way to make sure cold weather charging only takes place when there is a net gain to be had.

 

[merl]

For anyone who is following this, I have just come across this piece of info.
This suggests the heater should not have activated in the colder weather we had last month.

Looks like it's going to be later next week before it drops to 5 again so will keep an eye on it around then.

Personally I'd charge to say 30% and then completely disconnect from the van and see what happens when the temperature next drops to close to zero. By their own admission the heater should only cut in if there's a charge current flowing so if the battery loses it's charge while it's disconnected then the battery(BMS ) is obviously faulty.
They'll probably send you a new battery and let you keep the Duff one. Just replace the BMS and you'll have a nice spare to compensate for your hassle.

 

[Bat21]

Personally I'd charge to say 30% and then completely disconnect from the van and see what happens when the temperature next drops to close to zero. By their own admission the heater should only cut in if there's a charge current flowing so if the battery loses it's charge while it's disconnected then the battery(BMS ) is obviously faulty.
They'll probably send you a new battery and let you keep the Duff one. Just replace the BMS and you'll have a nice spare to compensate for your hassle.

Thanks Merl, good advice there which I had already thought of.

I will keep a close eye on it, temps don't seem to be dropping at the moment. We have 4c forecast on Boxing Day but as the battery is fairly insulated I doubt it will drop to the required 5c needed for the heater to activate if it is faulty.

Will report back once I know the battery has dropped below the 5c threshold.

 

[merl]

Thanks Merl, good advice there which I had already thought of.

I will keep a close eye on it, temps don't seem to be dropping at the moment. We have 4c forecast on Boxing Day but as the battery is fairly insulated I doubt it will drop to the required 5c needed for the heater to activate if it is faulty.

Will report back once I know the battery has dropped below the 5c threshold.

You could remove the battery from the van and sit it in a plastic storage container with a mixture of ice cubes and water, this will stabilise at 0 degrees eventually as long keep solid ice in the mixture.
Keep the water level just below the top, connect a multimeter and see what happens.