Dual battery top up

Submitted: Friday, Jan 04, 2019 at 16:18
ThreadID: 137648 Views:1164 Replies:10 FollowUps:12
Hello I am thinking of getting a dual battery setup in the engine bay but since the car is only doing short trips most times is that enough to keep your secondary battery charged? does anybody have a particular way of keeping it charged or do you not worry about it ?
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Reply By: Frank P (NSW) - Friday, Jan 04, 2019 at 17:11

Friday, Jan 04, 2019 at 17:11
I'm in the same situation, JK, with a dc-dc charger. My tourer is my run-around when at home and all it gets then is short runs. I don't charge the second battery other than by driving, except if I use it - fridge for a picnic or some such - then I'll give it a full charge to bring it up and then let the daily run-around look after it.

Battery is a 120Ah SSB AGM. I've had no problems, it's now 4 years old.

Cheers
AnswerID: 623023

Follow Up By: Johnnykluger - Friday, Jan 04, 2019 at 19:18

Friday, Jan 04, 2019 at 19:18
Frank may I ask how do you charge the battery when the car is not running do you take it out and charge it or do it from within the engine bay?
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Follow Up By: Frank P (NSW) - Friday, Jan 04, 2019 at 22:52

Friday, Jan 04, 2019 at 22:52
JohnnyK,

Firstly, I read your opening post to be asking about "between trips" with no load on the second battery. My assumption may have been wrong.

If you are asking about a touring situation with a load on your battery and short drives, then things are quite different.

Les-PK Ranger is, correctly, not making the assumption I made and is asking for confirmation.

I leave the battery in place for mains charging. When the engine is off the battery is isolated from everything else by the dc-dc charger. I have an Anderson going direct to the second battery. When I need to, I plug my mains charger into that. This also applies when I'm touring and need to top up.

If you choose not to use a dc-dc charger, just a solenoid-based isolator, it will do the same thing so you could charge from the mains the same way.

Now, if you're asking about touring with a fridge and other loads in use and doing short drives, then you would need something more than what I have said to supplement the charging from the short drives - solar or mains or generator.

Cheers
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FollowupID: 896103

Reply By: qldcamper - Friday, Jan 04, 2019 at 18:16

Friday, Jan 04, 2019 at 18:16
If your not running anything off it and have a dc dc charger fitted short runs will keep it just fine.
AnswerID: 623026

Follow Up By: Les - PK Ranger - Friday, Jan 04, 2019 at 18:47

Friday, Jan 04, 2019 at 18:47
That’s the thing isn’t it ?
No mention of why the 2nd battery is going in, what it’s task(s) might be, or how often it will be required in the field, so it is an unanswerable question until this is known.

Johnny, can you advise if short trips is daily touring, or around town, and what the 2nd battery will be expected to do / run ?
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FollowupID: 896095

Reply By: Johnnykluger - Friday, Jan 04, 2019 at 19:14

Friday, Jan 04, 2019 at 19:14
Car would be used mainly for day trips round town very short runs with the occasional trip away . Probably 4 times a year one week at a time and the occasional weekend away.
.
AnswerID: 623028

Follow Up By: Les - PK Ranger - Friday, Jan 04, 2019 at 19:55

Friday, Jan 04, 2019 at 19:55
Some of the info required.

What’s it going to be doing ?
Eg, why are you fitting 2nd battery ?

If you were running a fridge full time it’s very likely you won’t keep it topped off with those short drives.
This is running a VSR or preferably a decent dc-dc charger.
A small solar panel of 100w to 150w hooked up at home might be ok for those down times.
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FollowupID: 896098

Reply By: qldcamper - Saturday, Jan 05, 2019 at 09:47

Saturday, Jan 05, 2019 at 09:47
Lets ask the question again.
Will anything be running off of the second battery when in town and what do you refer to as short trips, is this car a daily driver or will it be parked up for extended periods??

You may be better off with a removable set up with the battery in its own box complete with dc dc charger.
AnswerID: 623033

Follow Up By: Johnnykluger - Sunday, Jan 06, 2019 at 16:04

Sunday, Jan 06, 2019 at 16:04
When in town I’ll be doing the short runs school shops etc , but it will be empty no fridge etc running off the battery.
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Follow Up By: qldcamper - Sunday, Jan 06, 2019 at 16:18

Sunday, Jan 06, 2019 at 16:18
If thats the case a dc dc unit such as a redarc 1225 lv will be more than enough to maintain the battery when not travelling without the need for mains charging.
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FollowupID: 896159

Reply By: RMD - Saturday, Jan 05, 2019 at 09:49

Saturday, Jan 05, 2019 at 09:49
Jihnny K
If you have a Kluger, then it almost certainly has an ECU controlled alternator, so simple solenoid linking to the second battery may never charge the aux batt properly.
Fitting a suitable DC DC charger matched for the purpose is good, BUT, if you are doing the short trips you mentioned in previous posts, then the DC DC charger will hardly have time to get it's brain sorted and begin appropriate charging before you switch off the engine at the end of the very short trip. DC DC chargers work on programmed time intervals and detected voltage level of main battery to decide what to do and when to begin charging the aux battery.
The DC DC will be good for almost all other normal longer run, useage though.

At home you can use an Anderson plug on a lead added to the aux battery and simply plug in a suitable 240v AC charger to charge and to deliver a similar charge profile to the aux battery or to top up prior to travelling. Charger needs to be modified to have an Anderson on it to make it simple.
I have a digital voltmeter across my batteries, aux battery included, so at a glance I can see if a charge is required or something has gone wrong with the normal systems.
AnswerID: 623034

Follow Up By: Zippo - Saturday, Jan 05, 2019 at 11:53

Saturday, Jan 05, 2019 at 11:53
As you would be aware, the ignition-sensing DC-DC chargers are able to get their act into gear right from the get-go (as distnct from the voltage-sensing ones) and will deal with an ECU-controlled alternator properly. That still leaves the issue of short runs, and the question of any load connected to the aux remains unclear.
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Follow Up By: HKB Electronics - Saturday, Jan 05, 2019 at 12:52

Saturday, Jan 05, 2019 at 12:52
Toyota ECU controlled? I believe you'll find the Kluger is fitted with a temperature compensated alternator. The only Australian Toyota model that I know of with ECU is the 2.8Ltr Prado.
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Follow Up By: RMD - Saturday, Jan 05, 2019 at 15:59

Saturday, Jan 05, 2019 at 15:59
That is good news.
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Reply By: Sigmund - Saturday, Jan 05, 2019 at 10:10

Saturday, Jan 05, 2019 at 10:10
Fitting a 2nd battery can crack the engine bay wall so check to see if others have done it successfully.
AnswerID: 623035

Reply By: HKB Electronics - Saturday, Jan 05, 2019 at 13:31

Saturday, Jan 05, 2019 at 13:31
Johnnykluger,

What type of dual battery system are you having fitted?

When you go away for a week what will you be running of the aux battery?

During the week your away how long are you camped out for without running the car?
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AnswerID: 623040

Reply By: smwhiskey - Saturday, Jan 05, 2019 at 22:01

Saturday, Jan 05, 2019 at 22:01
During the week, around town with no load on the battery I let the redarc handle the charge to the batteries.

Out bush or beach for a few days, with the camping lights and Waeco running off the aux battery, and doing little or no driving then I've generally got a 120w solar blanket sitting on the roof of the 4WD to provide additional charge.

Takes about 2 minutes to set the blanket up and I either plug it into the spare 12v socket in the cabin or the Anderson plug at the rear - both of which are directly connected to the aux battery.

So far no problems.

Simon
AnswerID: 623050

Reply By: Johnnykluger - Sunday, Jan 06, 2019 at 16:14

Sunday, Jan 06, 2019 at 16:14
Sorry I’d better clarify, I have just purchased a 2014 hilux for which the dual battery system is for . As for the problem of charging a solar panel permanently mounted to the roof connected to a dc-dc charger should solve the problem?
AnswerID: 623060

Follow Up By: Frank P (NSW) - Sunday, Jan 06, 2019 at 17:33

Sunday, Jan 06, 2019 at 17:33
JohnnyK,

Yes, but only if the dc-dc charger has a solar input. Not all dc-dc chargers have solar input, so make sure you buy the right one.

Qldcamper mentioned the Redarc BCDC1225. That would be fine. There are others.

Where do you plan to mount the second battery? Under the bonnet or elsewhere?

I ask because under the bonnet is an unsuitable location for most dc-dc chargers Including the BCDC1225, yet they should be mounted as close as practically possible to the battery they are charging. If you mount battery and charger in the tray (in a protective box) or canopy it makes things simpler.
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Follow Up By: HKB Electronics - Sunday, Jan 06, 2019 at 17:46

Sunday, Jan 06, 2019 at 17:46
You can use a VSR setup with a booster diode in that model.
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 06, 2019 at 18:05

Sunday, Jan 06, 2019 at 18:05
.
The Redarc BCDC1225 charger is only suitable for alternate solar input when wired with a changeover relay.

The BCDC1225-D has dual input.
Cheers
Allan

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Reply By: swampy - Monday, Jan 14, 2019 at 10:20

Monday, Jan 14, 2019 at 10:20
hi
dc/dc charger with mppt solar input as well.

Either solar panel on roof racks OR
Portable solar around the 150--160 watt

240v charging
Have an Anderson plug located just behind bumper and charge while home.
AnswerID: 623205

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