Recovering a flat lithium battery

Your battery has switched itself off to protect the cells. Here is how to bring it back.

Why the battery switched itself off

A lead-acid battery will happily let you drain it until there is nothing left, and it quietly damages itself on the way down. Lithium does not work like that, and TITAN batteries are built not to allow it.

Every TITAN has a BMS watching each cell individually. When the lowest cell reaches the bottom of its safe range, the BMS opens the discharge path and stops supplying current. Everything goes quiet. From where you are standing that looks like a dead battery, but it is the opposite: the battery has protected itself from the one thing that genuinely does shorten a cell's life, which is being run flat and left there.

So the shutdown is the safety net working exactly as designed. If it had not happened, you would have a real problem instead of a temporary one.

Has it been damaged?

No, provided it gets recharged reasonably soon. A pack that trips out and goes back on charge within a few days is completely unaffected. There is no lost capacity to recover and nothing to re-learn. You simply charge it and carry on.

What the cells do not like is being left sitting empty for weeks or months, which is worth knowing if this has happened at the end of a season. If your battery has been flat for a long time, still charge it, and then get in touch so we can take a look at the readings with you.

Waking it up

Step one: take the load off

Switch off whatever drained it. An inverter left on standby, a fridge, or a tracker are the usual suspects. This is not strictly required, but it means the battery is not fighting a load the moment it comes back, and it makes the next step more likely to work first time.

Step two: connect a charger

Any charger will do. Mains charger, solar through a controller, a DC to DC charger from the alternator, or a bench charger. As soon as the BMS sees charge voltage on the terminals it closes the circuit back up and the battery comes alive. The app usually reconnects within a few seconds of that happening.

Let it charge properly rather than just long enough to wake it. Taking it back to full also gives the BMS a chance to re-reference its percentage reading, which will very likely have drifted while all this was going on.

If the charger will not start

Some chargers look at the terminals first, see close to zero volts, decide there is no battery connected, and refuse to do anything. This is a quirk of the charger rather than a sign of a problem with the battery, and it catches people out because it feels like proof that the battery is dead.

Any of these will get you past it:

Use a different charger. Chargers vary enormously in how fussy they are about this. Many will start into a pack that another has refused.
Use a DC to DC charger. If you have one fitted from the alternator, run the engine. These are generally the least fussy of the lot.
Check for a lithium or an AGM mode. Some chargers only perform the low-voltage check in certain profiles, so switching mode is occasionally all it takes.
Give us a call. We do this often and there are a couple of further options depending on which battery you have. It is a quick conversation.

Stopping it happening again

Most flat batteries we see come down to one of three things, and all of them are fixable.

Something was drawing power that nobody knew about. Inverters in particular can pull a surprising amount doing nothing at all. The Energy Flow view in the TITAN app is good at catching these, because it shows you what is being consumed when you believe everything is switched off.
The charging was not keeping up. Common in winter, when solar yield collapses and the battery is slowly losing ground week by week rather than being flattened in one go.
The vehicle was left standing. Small standby loads over several months add up to a lot.

If you are not sure which of these applies to you, the app's history will usually make it obvious, and we are happy to look through it with you.

If you are still stuck

If the battery will not wake with any charger, or it wakes and trips straight back out on a full pack, stop there and contact us. Do not open the battery, and do not let anyone else open it either.

Every TITAN carries a lifetime warranty, and that cover is fully transferable if the vehicle changes hands. A battery that has protected itself and will not come back is exactly the sort of thing we want to hear about, so please do not sit on it. Have the battery ID from the label to hand if you can, since it lets us pull up the history straight away.