Just some late night thoughts. I’m planing to install the Slee dual battery kit with a battery isolator. But the alternator in my 97 has only the 80 amp stock alternator. If I run this set up will it damage the alternator? Or does the stock alternator has the power to charge two battery at the same time?
Can I run dual battery with stock alternator?
- Thread starter timchen
- Start date
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Yes, you can. On diesel land cruisers stock alternator 80A and two batteries.
CaptClose
SILVER Star
I run the same setup on my 97 with a stock alternator. I’ve had zero issues. Works flawlessly.
SmokingRocks
hopelessly addicted to Cruisers
Well I have three batteries on the stock alternator and my rig hasn't gone nuclear. So theres that....
I mean this in the nicest way but it sounds you don't know much about electrical systems, because the size of alternator has nothing to do with how many batteries you want to run. Let me try to draw som easy to understand comparisons to explain this.
Electricity is just like water, the water plant produces clean water (Millions of Gallons per day aka MGD) and pumps it into water towers waiting for you to turn on your shower or whatever. This more or less the same as what happens in your car, the alternator produces electricity (80 amps & 14v) that it stores in the batteries (tanks) until you need to use it. Volts = the pressure pushing the power through the pipeline, AMPS = the measurement of energy moving through (think of this as a flow rate, like gallons per minute), Ohms = restriction due to the "pipeline" this could be due to a resistor or a long run of small diameter wire.
Taking it a step further the transmission pipelines from the water plant to the water tower are the same as the wires from your power source to the final device. A larger pipe will flow more water, a larger wire will flow more AMPS (current), smaller pipes will cause restriction and flow less water, smaller wires will restrict (more Ohms) and lessen the flow which equals less AMPS passing through.
So if the water level in the water tower gets too low the plant can only fill it so fast, how could this cause damage to the plant? It can't.
Same goes for your alternator if the batteries are low on charge the alternator will still pump all the amps it can back into them.
This is a helpful image
I mean this in the nicest way but it sounds you don't know much about electrical systems, because the size of alternator has nothing to do with how many batteries you want to run. Let me try to draw som easy to understand comparisons to explain this.
Electricity is just like water, the water plant produces clean water (Millions of Gallons per day aka MGD) and pumps it into water towers waiting for you to turn on your shower or whatever. This more or less the same as what happens in your car, the alternator produces electricity (80 amps & 14v) that it stores in the batteries (tanks) until you need to use it. Volts = the pressure pushing the power through the pipeline, AMPS = the measurement of energy moving through (think of this as a flow rate, like gallons per minute), Ohms = restriction due to the "pipeline" this could be due to a resistor or a long run of small diameter wire.
Taking it a step further the transmission pipelines from the water plant to the water tower are the same as the wires from your power source to the final device. A larger pipe will flow more water, a larger wire will flow more AMPS (current), smaller pipes will cause restriction and flow less water, smaller wires will restrict (more Ohms) and lessen the flow which equals less AMPS passing through.
So if the water level in the water tower gets too low the plant can only fill it so fast, how could this cause damage to the plant? It can't.
Same goes for your alternator if the batteries are low on charge the alternator will still pump all the amps it can back into them.
This is a helpful image
I have 2 batteries with stock alternator and dual battery management system - No problems
It starts by charging the main engine battery and only when the main battery is charged enough only then the secondary battery get connected and charged
It starts by charging the main engine battery and only when the main battery is charged enough only then the secondary battery get connected and charged
The OEM alternator in a 91/92 FJ80 with external fan was 80 amp.
The OEM alternator in a late 92 with internal fan was 90 amp.
The OEM alternator in an FZJ80 was 90 amp.
Folks run dual battery systems in older Cruisers with the OEM 60 amp alternator.
I question the need for a dual battery system in the first place, but I like to keep things simple.
The OEM alternator in a late 92 with internal fan was 90 amp.
The OEM alternator in an FZJ80 was 90 amp.
Folks run dual battery systems in older Cruisers with the OEM 60 amp alternator.
I question the need for a dual battery system in the first place, but I like to keep things simple.
Hello, I'm new here but figured why not jump in and contribute. I am a certified marine electrician so I work on boats/yachts often set up for long range cruising with big battery banks and sometimes sophisticated alternator setups.
Your electrical concepts and explanations are sound but there is a point at which the alternator can/will be damaged by charging large battery banks.
Please understand that I am only saying there is a point where you can damage the alternator with a large battery bank. A simple two battery setup is fine especially if the batteries are only used for starting so very limited amp-hours required to recharge. Even if the 2nd battery is a deep cycle used to run refrigeration for example you could have at most 100 amp-hours or so of charging to do so this would work the alternator hard for only the first hour or so then charge rates would slow.
The problem is heat. An OEM alternator is designed to replenish the amp-hours taken from the starting battery to start the vehicle and to support the minor electrical loads of the vehicle when it is running. An OEM alternator may be rated at 80 amps, which is a good bit, but it is not designed for continuous duty at or even near the rated output level. The "dumb" internal regulators in a basic OEM alternator have no means to do temperature compensation so they will gladly run the alternator to catastrophic thermal failure if there is enough depleted battery capacity to overwork the alternator.
Here is a OEM alternator in a marine application that was connected to a huge deep cycle battery bank. The batteries were large enough that the alternator was working at full output for hours and hours. Each day, if the batteries are cycled overnight, the alternator gets worked hard again. Over time it is too much for an OEM design.
We often upgrade alternators to aftermarket units rated for continuous duty and with intelligent regulation including temperature compensation based on both alternator temp and battery temp.
SmokingRocks
hopelessly addicted to Cruisers
You are correct. I opt’d to leave out that info because not many of us are hauling around a battery bank designed to provide power to a yacht. Can’t imagine how heavy that would make my already 7,000lb rig...
