Trickle charging starter battery in RV

[Solarfun4jim]

My RV (under conversion) from a minibus has a parasitic drain from a tachograph which is now obsolete from purpose, but cannot easily be removed because it generates the speed signal/odometer reading etc. I'm noticing that within a week of not driving, the starter battery gets to the point it wont crank over. I have purchased a 100W panel and a small PWM charger to trickle charge the SLA battery whilst it sits there. What are the ideal charging and float values i should dial in to the charger? Think i read somewhere 14.1v for bulk and float, but it would be nice to have that confirmed. (another post on a thread stated 14.4v, so i'm looking for confirmation on whats best)
Second question is, does the charger need to be connected direct to the battery or can it be connected to the 'jump start terminals' in the engine bay. To let you understand, the starter battery is located inside the vehicle in a compartment which is less easy to access.

Thanks.

 

[snoobler]

It really depends on the battery. I would shoot for 14.4V on an AGM, but you'd do better to find the charge parameters for your battery.

Doesn't have to be connected to the battery, but it's more effective that way. You could connect anywhere that reaches the battery, but you'll have a voltage drop between the point charge is applied and the battery terminals due to the resistance in the wiring.

 

[Solarfun4jim]

It really depends on the battery. I would shoot for 14.4V on an AGM, but you'd do better to find the charge parameters for your battery.

Doesn't have to be connected to the battery, but it's more effective that way. You could connect anywhere that reaches the battery, but you'll have a voltage drop between the point charge is applied and the battery terminals due to the resistance in the wiring.

Thanks snoobler,
It is a maintainence free lead acid, so think i will shoot for 14.1v to be on the safe side.
It is only to keep the starter battery topped up whilst is sits through the winter.

 

[RCinFLA]

You will destroy battery continously floating at 14.4v.

13.6 to 13.8v is more appropriate.

You can check manufacturer's spec.

 

[Solarfun4jim]

You will destroy battery continously floating at 14.4v.

13.6 to 13.8v is more appropriate.

You can check manufacturer's spec.

@RCinFLA
Thanks RCinFLA, i couldn't seem to get a data sheet on the battery....but i will adjust as advised. I had set it to 14.1v, but so long as it maintains the battery at 13.7v then i'm happy with that. Thanks for taking the time to highlight this.

 

[snoobler]

Ummm... I missed the float part. When you said 14.1V for bulk, I apparently stopped reading.

RCinFLA is absolutely correct.

13.2V is also another common float voltage. Some recommendations are for 13.2 over 13.5 due to accelerated electrolyte loss over long periods of float. My Trojans also call for a 13.2V float.

 

[mikefitz]

I guess you have a Fiat Ducato/Citroen Relay/ Peugeot Boxer base vehicle. (similar to the US Promaster).
The jump start terminals are directly connected with heavy duty cables to the engine battery via a high current rating CAL4 fuse at the positive battery post.
Since your vehicle is a minibus there is a good chance it has the optional 'converters outlet' under the black plastic cover at the bottom of the drivers side B post ( the one that houses the seat belt mechanism).
The connector with the thick wires is fused at 50A at the engine battery, you could connect at that point.
Very carefully check the performance of any PWM low cost controller you may fit, many have a high 13.8 volt float or never actually get into float stage, charging at 14.4 volts continually.

It you are fitting house batteries with solar charging there are a number of low cost units that connect between the house battery and the engine battery,

Votronic 3065 Battery Master - Standby-charger 12V

<p>This Votronic charger is a great way to trickle charge your engine battery in a motorhome, Installed between the starter battery and the leisure...

www.roadpro.co.uk

If you need more info on the engine battery fuses and connections or the converters outlet I can provide.

Mike

 

[HRTKD]

It sounds like the circuit for your tachograph is connect to an always on fuse. Would it be possible to change it to an ignition on fuse?

 

[Samsonite801]

My RV (under conversion) from a minibus has a parasitic drain from a tachograph which is now obsolete from purpose, but cannot easily be removed because it generates the speed signal/odometer reading etc. I'm noticing that within a week of not driving, the starter battery gets to the point it wont crank over. I have purchased a 100W panel and a small PWM charger to trickle charge the SLA battery whilst it sits there. What are the ideal charging and float values i should dial in to the charger? Think i read somewhere 14.1v for bulk and float, but it would be nice to have that confirmed. (another post on a thread stated 14.4v, so i'm looking for confirmation on whats best)
Second question is, does the charger need to be connected direct to the battery or can it be connected to the 'jump start terminals' in the engine bay. To let you understand, the starter battery is located inside the vehicle in a compartment which is less easy to access.

Thanks.

My first question about this tachograph device, is why is it producing a parasitic drain (presuming it is wired in properly)? I might check the model of the unit and look up the wiring diagram for it to make sure about how it should be correctly interfaced to the vehicle.

Ok so perhaps it has a battery-constant power feeding it, and then an ignition-trigger wire feeding it to wake it up while key is in run position (based on my assumption, or maybe has single power lead only to have power when key is in run position). Usually when you shut off the key it should not drain on the battery as the device is off (standby), or power is completely removed from the device.

Now if it is wired correctly (according to manufacturer specification), and it still has some kind of draw/drain on the battery, then couldn't we just wire in all connections to break to the device when key is turned off (either direct wiring or through a relay if needed)?

I guess I'm not understanding why this device must create a parasitic drain if it doesn't need to. Especially if I had a vehicle that regularly sits most the time, I would just remove all parasitic drains. Or put a main battery disconnect switch on it so I could disconnect the battery when I plan to park it for days.

Maybe there is a simple explanation on why you wouldn't be able to eliminate the key-off battery drain but I felt like I ought to bring this question up out of curiosity.

 

[Samsonite801]

It sounds like the circuit for your tachograph is connect to an always on fuse. Would it be possible to change it to an ignition on fuse?

You beat me to it I had the same wondering.... I left my question posted above anyways, basically same thing as you were thinking... (i just didn't refresh the page and see your post until I posted later)

 

[HRTKD]

You beat me to it I had the same wondering.... I left my question posted above anyways, basically same thing as you were thinking... (i just didn't refresh the page and see your post until I posted later)

Great minds think alike.

The other thought I had was to put in a relay to turn on that circuit when the ignition came on.

 

[Solarfun4jim]

I guess you have a Fiat Ducato/Citroen Relay/ Peugeot Boxer base vehicle. (similar to the US Promaster).
The jump start terminals are directly connected with heavy duty cables to the engine battery via a high current rating CAL4 fuse at the positive battery post.
Since your vehicle is a minibus there is a good chance it has the optional 'converters outlet' under the black plastic cover at the bottom of the drivers side B post ( the one that houses the seat belt mechanism).
The connector with the thick wires is fused at 50A at the engine battery, you could connect at that point.
Very carefully check the performance of any PWM low cost controller you may fit, many have a high 13.8 volt float or never actually get into float stage, charging at 14.4 volts continually.

It you are fitting house batteries with solar charging there are a number of low cost units that connect between the house battery and the engine battery,

Votronic 3065 Battery Master - Standby-charger 12V

<p>This Votronic charger is a great way to trickle charge your engine battery in a motorhome, Installed between the starter battery and the leisure...

www.roadpro.co.uk

If you need more info on the engine battery fuses and connections or the converters outlet I can provide.

Mike

Thanks Mike.
Minibus is based on a VW crafter. I toyed with the idea of using a SSR between the ignition circuit and the tacho feed, but on reading some forums, some people were experiencing error codes etc....so i decided on KISS. The PWM controller i got was inexpensive, but i can limit the 'stop charging' setting to 13.2V , which i assume is enough to keep the starter battery topped up sufficiently over winter. We don't get sun every day, plus when we do get it, it is weak/watery, but hopefully enough amps generated to do the job.

 

[Solarfun4jim]

My first question about this tachograph device, is why is it producing a parasitic drain (presuming it is wired in properly)? I might check the model of the unit and look up the wiring diagram for it to make sure about how it should be correctly interfaced to the vehicle.

Ok so perhaps it has a battery-constant power feeding it, and then an ignition-trigger wire feeding it to wake it up while key is in run position (based on my assumption, or maybe has single power lead only to have power when key is in run position). Usually when you shut off the key it should not drain on the battery as the device is off (standby), or power is completely removed from the device.

Now if it is wired correctly (according to manufacturer specification), and it still has some kind of draw/drain on the battery, then couldn't we just wire in all connections to break to the device when key is turned off (either direct wiring or through a relay if needed)?

I guess I'm not understanding why this device must create a parasitic drain if it doesn't need to. Especially if I had a vehicle that regularly sits most the time, I would just remove all parasitic drains. Or put a main battery disconnect switch on it so I could disconnect the battery when I plan to park it for days.

Maybe there is a simple explanation on why you wouldn't be able to eliminate the key-off battery drain but I felt like I ought to bring this question up out of curiosity.

The tacho unit was factory fitted. There are several forum entries about the constant drain on the battery. Not sure about the legalities of tampering with it(even although it is now a non requirement, through change of use of the vehicle). It is still directly liked to odometer and any tampering with this could invalidate MOT. Since i dont know enough about it, i couldn't make a fully informed decision on takling the tacho, so next best was to simply compensate....hence the solar panel route.