Charging auxiliary batteries
- Thread starter fg4oz
- Start date
Some things to think about:
what type of batteries? AGM, flooded?
will off-gassing be an safety/space issue?
what's the total amp hour capacity of your aux batts?
what's the amp output of your alt?
some batts like to be charged multi-stage, instead of over-cooking them, they last longer.
There are a few different brands of multi-stage controllers for automotive/marine use.
Charging time= CAP X DOD divided by CC X 80
CAP= batt capacity
DOD=depth of discharge
CC = current charge in amps (charge current depends on batt size)
what type of batteries? AGM, flooded?
will off-gassing be an safety/space issue?
what's the total amp hour capacity of your aux batts?
what's the amp output of your alt?
some batts like to be charged multi-stage, instead of over-cooking them, they last longer.
There are a few different brands of multi-stage controllers for automotive/marine use.
Charging time= CAP X DOD divided by CC X 80
CAP= batt capacity
DOD=depth of discharge
CC = current charge in amps (charge current depends on batt size)
If it charges your starter battery it will charge your aux batteries ok, the current output of the alternator will govern how quick the batteries charge, you need at least 13.5 for the redarc smart solenoid to work correctly, if you want to charge the batteries to 100% charge then use a DC to DC charger as made by Redarc and others, a low voltage disconnect unit is always a good idea and will give you longer battery life.
blackduck
Explorer
Ben how big are the batteries?
my FG managed to keep the 2 lead acid starters, one 120Ah AGM house and the 4 x 120Ah AGM caravan batteries charged without a drama (with a little help from the solar)
its not so much a question of can they be charged its more whats the drawing rate of the slide on
if your going to drag the guts out of the battery on a regular basis you'll have to do a lot of driving to keep them charged
my FG managed to keep the 2 lead acid starters, one 120Ah AGM house and the 4 x 120Ah AGM caravan batteries charged without a drama (with a little help from the solar)
its not so much a question of can they be charged its more whats the drawing rate of the slide on
if your going to drag the guts out of the battery on a regular basis you'll have to do a lot of driving to keep them charged
Thanks for the feedback. I have a bit more research to do. Only running a 40L engel for now with the option of a second either as a freezer or second fridge. And two or three strip led lights. One battery dedicated to the linak motor. Charger outlet for mobile phone. No other gadgets. Trying to go as simple as possible. The safety aspect concerns me. Do all batteries give off gas?
westyss
Explorer
Ill just post some of what I experienced with this topic.
I found that the altenator was insufficient to charge my aux batteries in the standard set up due to the regulator seeing adequate volts of the main batteries and as a result only trickle charged the aux batts, over time they appeared to be charged but they were not 100% charged.( I have four 245amp/hr 6 volt aux batteries ) So I went out and got a battery to battery charger that tricks the alt regulator into thinking that there is not sufficient volts and continues to put out good amps to the batteries that gets sent to the aux batteries to fully charge them using a three stage charge. The unit also functions as a separator. I used a sterling product but have seen other makes but they are pricey, mine was around $250, after installing that unit the batteries got a nice solid amp load into the aux batteries and fully charged them so at this time appears to work well. The only issue I had was that it overheated during the summer while not driving and went into standby mode( self protection) but has not overheated again yet so seems like it needs to be used a bit to get things working well. I installed it last summer and it is an item that I dont even look at anymore so low maintenance.
If you have low load draws the batteries will charge okay but with a load the charge will be inadaquate.
I found that the altenator was insufficient to charge my aux batteries in the standard set up due to the regulator seeing adequate volts of the main batteries and as a result only trickle charged the aux batts, over time they appeared to be charged but they were not 100% charged.( I have four 245amp/hr 6 volt aux batteries ) So I went out and got a battery to battery charger that tricks the alt regulator into thinking that there is not sufficient volts and continues to put out good amps to the batteries that gets sent to the aux batteries to fully charge them using a three stage charge. The unit also functions as a separator. I used a sterling product but have seen other makes but they are pricey, mine was around $250, after installing that unit the batteries got a nice solid amp load into the aux batteries and fully charged them so at this time appears to work well. The only issue I had was that it overheated during the summer while not driving and went into standby mode( self protection) but has not overheated again yet so seems like it needs to be used a bit to get things working well. I installed it last summer and it is an item that I dont even look at anymore so low maintenance.
If you have low load draws the batteries will charge okay but with a load the charge will be inadaquate.
westyss
Explorer
lead acid batteries emit hydrogen while charging so need to be vented, sealed batteries as in AGM will not and can be installed inside or on its side, I would stay away from dedicating batteries for an item just to make sure all the batteries recieve an equal chargeand discharge.And "go big or go home" as in plan for more usage because you will always add more load and the batteries will always slowly deteriorate.
Alastair D(Aus)
aging but active
Battery to Battery chargers
I am in the middle of a camper build on an Isuzu NPS 300 chassis and had the same charging decision to make. This is further complicated by the starter battery system being 24v and the house batteries being 12v.
After much searching I decided on the Redarc BCDC1240 for the following reasons.
1. It will accept power from the 24v system and put out up to 40A to the 12v system.
2. It acts as a smart system isolating the house batteries when the engine is off.
3. It does 3 stage charging rather than a dumb feed so makes better use of the alternator.
4. It has an MPPT solar regulator built in
5. It is Aus made from a company that I have found gives excellent backup to their products
6. It has settings for different battery types - wet,AGM,Ca etc and so maximises the charge
7. It is compact and designed to be robust
8. It kept the system relatively simple - until I added other things !!
It is similar to the Sterling product but I chose the Redarc unit because of no 5 above. The units are quite expensive but if you search there are suppliers selling at well below list price with full Redarc warranty. See link below for info.
http://www.redarc.com.au/products/product/in-vehicle-battery-charger-40a/
I have no connection to Redarc etc but have have had very good experiences with their products over the years.
cheers
I am in the middle of a camper build on an Isuzu NPS 300 chassis and had the same charging decision to make. This is further complicated by the starter battery system being 24v and the house batteries being 12v.
After much searching I decided on the Redarc BCDC1240 for the following reasons.
1. It will accept power from the 24v system and put out up to 40A to the 12v system.
2. It acts as a smart system isolating the house batteries when the engine is off.
3. It does 3 stage charging rather than a dumb feed so makes better use of the alternator.
4. It has an MPPT solar regulator built in
5. It is Aus made from a company that I have found gives excellent backup to their products
6. It has settings for different battery types - wet,AGM,Ca etc and so maximises the charge
7. It is compact and designed to be robust
8. It kept the system relatively simple - until I added other things !!
It is similar to the Sterling product but I chose the Redarc unit because of no 5 above. The units are quite expensive but if you search there are suppliers selling at well below list price with full Redarc warranty. See link below for info.
http://www.redarc.com.au/products/product/in-vehicle-battery-charger-40a/
I have no connection to Redarc etc but have have had very good experiences with their products over the years.
cheers
blackduck
Explorer
geez ben when you said 3 batteries I figured you were setting up for a ton of load
your fridge will probably draw 35 amps a day and that's probably giving it 5 amps more than it will and your lights etc will draw bugger all
youd probably get away with one decent 120Ah AGM instead of 3 lesser batteries
don't forget with batteries you get what you pay for a good battery will cost you 5 to 600 dollars
don't go down the "marine "battery road, great for starting boats not much chop for running fridges
something else to consider is a couple of light solar panels on the roof of the camper or my preferred option a folding panel
with your usage youd probably get away with 120w
Ruderacing
New member
Hi, the best way i found was a dc-dc aftermarket charger. I used a redarc multi stage dc-dc with a built in solar panel regulator that switches over when the vehicle is off. Never need to worry about my batteries now.
gait
Explorer
I've also used a Sterling B2B charger for the last 4 years. In parallel with 600w solar through MPPT regulator. Sterling also monitors alternator temperature. Just one of many solutions. More recent may be combined alternator regulator / 3 stage charger.
Alternator regulator voltage was too variable to reliably charge house batteries rapidly. For my AGM house batteries I like around 14.2v. With heavy load on alternator I measured as low as 13.7v.
Starting is a few seconds of high current which takes the alternator a few minutes to recharge. Part of the need is to avoid boiling the starter batteries. House use is a lot of hours of relatively low current which takes several hours to recharge - a lot of driving, a different charging problem.
In detail, the Sterling is rated at 50A input current which works out at about 38A to the house battery. Also it rests for 3 minutes every 20 minutes or so which reduces the average output. When house battery is heavily discharged and low sunlight I bypass the B2B and charge directly from alternator, until battery is charged to the point that the B2B is better (around 60% SOC). All that was important to me as I only usually need it when I'm camping in the rain and may need to top up house batteries as quickly as possible using engine ticking over / not moving.
The parallel connection of B2B and solar regulator with appropriate settings means solar is used in preference and alternator if insufficient solar (rather than only one or t'other).
Alternator regulator voltage was too variable to reliably charge house batteries rapidly. For my AGM house batteries I like around 14.2v. With heavy load on alternator I measured as low as 13.7v.
Starting is a few seconds of high current which takes the alternator a few minutes to recharge. Part of the need is to avoid boiling the starter batteries. House use is a lot of hours of relatively low current which takes several hours to recharge - a lot of driving, a different charging problem.
In detail, the Sterling is rated at 50A input current which works out at about 38A to the house battery. Also it rests for 3 minutes every 20 minutes or so which reduces the average output. When house battery is heavily discharged and low sunlight I bypass the B2B and charge directly from alternator, until battery is charged to the point that the B2B is better (around 60% SOC). All that was important to me as I only usually need it when I'm camping in the rain and may need to top up house batteries as quickly as possible using engine ticking over / not moving.
The parallel connection of B2B and solar regulator with appropriate settings means solar is used in preference and alternator if insufficient solar (rather than only one or t'other).
The only problem we have experienced with the Redarc DC -DC Chargers is they shut down at 80c so be careful where you mount them! under most bonnets its well over 80c.
westyss
Explorer
The Sterling DC-DC charger I have also doesnt like it hot or will go into "cool down mode", good ventilation is needed as the unit gets warm.
Alastair D(Aus)
aging but active
Overheating
Alan,
I am making a section of the underbed section of the camper an electrical box that will have a thermostatically controlled fan. I want to keep all the major stuff - BCDC, charger, inverter, switches & relays etc high and dry and cool. It will vent through a filter and I will have a switch so that I can turn the fan off at night in hot weather if necessary. We tend to do most of our major travelling in the cooler times of the year so I thinkl all will be ok.
cheers
Alan,
I am making a section of the underbed section of the camper an electrical box that will have a thermostatically controlled fan. I want to keep all the major stuff - BCDC, charger, inverter, switches & relays etc high and dry and cool. It will vent through a filter and I will have a switch so that I can turn the fan off at night in hot weather if necessary. We tend to do most of our major travelling in the cooler times of the year so I thinkl all will be ok.
cheers
Alastair D(AUS)
In lieu of getting a DC/DC converter, why wouldn't you just feed the inverter, from the alternator & plug a multi stage battery charger into the inverter. If you are ever plugged into 240v mains power, you can then remove the battery charger from the inverter & plug into mains
Rick
In lieu of getting a DC/DC converter, why wouldn't you just feed the inverter, from the alternator & plug a multi stage battery charger into the inverter. If you are ever plugged into 240v mains power, you can then remove the battery charger from the inverter & plug into mains
Rick