Battery woes complicated further by SpaceDrive

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Battery woes complicated further by SpaceDrive

Postby mattross » 01 Jan 2021, 13:40

As seems to be the topic of the month, I'm having issues with my VW Caddy batteries. It has a rear entry ramp and SpaceDrive 4-way joystick amongst other adaptions. I've been trying to drive it at least once a week, despite not having anywhere I'm allowed to go, since March 2020. Anyway, this morning I could tell as the ramp descended that the main battery was flat. It wouldn't start at all and then the suspension and ramp were down. At least the ramp can be manually moved so the car is locked at least, but now I'm thinking about charging solutions.

Firstly, is it okay to do a normal jump start to get the diesel engine running so it can start recharging? I have an AA battery conditioner (https://www.argos.co.uk/product/7604351) which I think I can run from a weatherproof socket to under the bonnet via my letterbox about 10M away, across a public footpath with a cable protector and some hi-vis tape. It wouldn't be on for more than 12 hours during the day once a week I'd guess, as I don't think leaving it permanently connected is a good idea.

Where it gets more complicated (because I'm not clued up about these things) is the secondary SpaceDrive battery. It gets replaced every two years (as the servicing company insist it must be) but is now overdue a replacement. I believe it's a Li-Ion unit, and by the replacement cost I suspect it's coated in 24 karat gold. It probably doesn't need replacing I'm sure and this morning the joystick was responding correctly so it's fine at the moment. I do worry about it a lot though, with it having my life in its hands every time I drive. Anyway, on the SpaceDrive module in the back of the car it has a button that can change the SpaceDrive battery from 'drive' to 'charge' mode. My interests relate to how this is likely to affect the AA charger and main battery if I hook them up and switch the SpaceDrive battery to charge mode. I have no technical information on how the two batteries are connected, if they are. A web search has given no clues as to how SpaceDrive works in this respect.

I'd be grateful for any advice.
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Re: Battery woes complicated further by SpaceDrive

Postby Burgerman » 01 Jan 2021, 17:27

Firstly, is it okay to do a normal jump start to get the diesel engine running so it can start recharging?

Yes. If we are talking about the vehicle starter battery. Be aware that deeply discharging a starter battery even once does it no good at all. Allowing it to slowly discharge while its parked up by the vehicle itself, and any extra equipment such as you have fitted, will also allow it to discharge all of the time slowly. Causing more long term damage to this starter battery. I suspect its already past its best. And yes it should be charged now FULLY with a decent 3 stage charger, for at least 24 hours preferably a couple of days. Better still replace it, and then fully charge before use. And add a solar charger panel on roof, and a charge controller. Theres a thread here already about this!

I have an AA battery conditioner (https://www.argos.co.uk/product/7604351) which I think I can run from a weatherproof socket to under the bonnet via my letterbox about 10M away, across a public footpath with a cable protector and some hi-vis tape. It wouldn't be on for more than 12 hours during the day once a week I'd guess, as I don't think leaving it permanently connected is a good idea.


That appears to be - from very dumbed down info, a 1A trickle charger. It will take anything from a few hours, to 70 to 100 hours to charge your battery depending in battery size and depth of discharge. It appears to have no voltage limit or 2 or 3 stage charge so leave it too long and batery will get cooked. Leave it not long enough and it will not be fully charged. Also 10 meters is much too far to extend the low voltage side. You need to use an AC extension cable with the charger at the car. Leaving a GOOD 3 stage charger permanantly connected IS a good idea.

No idea how space drive works.
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Re: Battery woes complicated further by SpaceDrive

Postby Burgerman » 01 Jan 2021, 17:30

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Re: Battery woes complicated further by SpaceDrive

Postby rover220 » 01 Jan 2021, 18:26

Make sure you do not connect the negative lead of the charger direct to the battery. Must go to chassis somewhere otherwise you will upset the battery monitoring system.
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Re: Battery woes complicated further by SpaceDrive

Postby Burgerman » 01 Jan 2021, 19:42

On a car main vehicle battery? It cant. The vehicle battery is negative earth/ground with a big fat cable. And so the battery is connected directly to the chassis. The batt negative is at the same potential as the vehicle chasis. My solar charger on the roof for e.g has the neg and pos connected to the same chassis ground and the permanant live that connects to the ramp computer in the rear.
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Re: Battery woes complicated further by SpaceDrive

Postby rover220 » 01 Jan 2021, 21:28

Burgerman wrote:On a car main vehicle battery? It cant. The vehicle battery is negative earth/ground with a big fat cable. And so the battery is connected directly to the chassis. The batt negative is at the same potential as the vehicle chasis. My solar charger on the roof for e.g has the neg and pos connected to the same chassis ground and the permanant live that connects to the ramp computer in the rear.


Not on most modern stuff especially vw. There is a shunt mounted directly to the neg terminal that the charging and battery management system uses to keep an eye on battery level, I am assuming the caddy in question has stop start but it should have.

The battery is maintain at 80% charge in normal use to allow headroom for the high voltages and surges produced under braking regeneration. This is also why batteries don't last long with additional loads such as door opening actuators.

If you connect your charger direct to neg terminal you will mess up the system as it will not be able to account for amps in and out correctly. This is also why if you have a new battery fitted the system should be programmed to tell it you have fitted a new one.
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Re: Battery woes complicated further by SpaceDrive

Postby Burgerman » 02 Jan 2021, 00:56

But a lead battery should never be maintained at 80%. Because it will sulfate and die rapidly. Not sure how that shunt thing works on stop start, but the battery must be charged to 100% as you decelerate or brake. Or the batt will soon die. As you drive it will stop charging temporarily to reduce load on the alternator for more miles per gallon. During these periods it may let the volts fall to save fuel.

Also not sure what you mean by regeneration. Most non electric or non hyybrid cars dont do regeneration as such. But they disconnect the alternator in cruise or accellerate. And reconnect it as you decelerate. So some fossil fuel cars only charge the battery as you decelerate to add load to the motor via the alternator, and remove that load as you accelerate or cruise by having no back EMF at the alternator. As you drive in cruise they allow the vehicle to run on the battery for all its electrical needs until it gets down to x volts, maybe 11.8?? Then it tops it up regardless if you never brake or decelerate. So there are times that you are driving on a less than full battery. But its fully charged to desulfate when you next start up or do a long drive. Or every single time you brake or decelerate. Just not continuously.

That shunt is to measure battery load or charge current as you drive. Charge or discharge at say 30A and it will show a few mV difference to allow the car to read current. Its a very low impedance / low resistance device, the external charger or battery will not know its there if you charge via solar/charge controller or a battery charger and will work properly. And the car doesent care as it sees state of charge by voltage when you turn it on. It may take a minute to relearn as you drive a mile.

Connecting a charger to a chassis or a battery terminal will still allow the sensor to work properly as long as you are not driving it around, and charging at a significantly higher rate than a solar panel/charger could do at the same time. You shouldnt connect say spot lights to the battery directly however as that will make the cehicle see a lower battery voltage and with no additional amps while driving. So will confuse the part that tells the alternator how to charge the battery as you drive. It will not hurt to charge the battery or leave a maintainance charger connected when not in use connected to the chassis or the battery.

Heres a bit more. https://www.samarins.com/glossary/battery-sensor.html
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