body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 800px;
margin: 0 auto;
padding: 20px;
}
.calculator-container {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}
.calc-title {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
}
.form-group {
margin-bottom: 20px;
}
.form-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #495057;
}
.input-wrapper {
position: relative;
}
.input-wrapper input {
width: 100%;
padding: 12px;
font-size: 16px;
border: 1px solid #ced4da;
border-radius: 4px;
box-sizing: border-box;
}
.currency-symbol {
position: absolute;
left: 12px;
top: 12px;
color: #6c757d;
}
.input-with-icon {
padding-left: 30px !important;
}
button.calc-btn {
width: 100%;
padding: 14px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.2s;
}
button.calc-btn:hover {
background-color: #0056b3;
}
#result-container {
margin-top: 25px;
background: #fff;
border: 1px solid #dee2e6;
border-radius: 4px;
padding: 20px;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
padding-bottom: 10px;
border-bottom: 1px solid #eee;
}
.result-row:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
color: #6c757d;
}
.result-value {
font-weight: bold;
font-size: 1.1em;
}
.final-cost {
color: #dc3545;
font-size: 1.3em;
}
.credit-amount {
color: #28a745;
font-size: 1.3em;
}
.article-content h2 {
color: #2c3e50;
margin-top: 30px;
}
.article-content ul {
margin-bottom: 20px;
}
.article-content li {
margin-bottom: 10px;
}
.info-box {
background-color: #e2e3e5;
padding: 15px;
border-left: 5px solid #6c757d;
margin: 20px 0;
}
function calculateWarranty() {
// Get input values
var priceInput = document.getElementById('batteryPrice');
var warrantyInput = document.getElementById('totalWarranty');
var ageInput = document.getElementById('monthsUsed');
var resultDiv = document.getElementById('result-container');
var usageDisplay = document.getElementById('usagePercent');
var creditDisplay = document.getElementById('creditAmount');
var costDisplay = document.getElementById('customerCost');
var statusMsg = document.getElementById('warranty-status-msg');
// Parse values
var price = parseFloat(priceInput.value);
var totalMonths = parseFloat(warrantyInput.value);
var usedMonths = parseFloat(ageInput.value);
// Validation
if (isNaN(price) || isNaN(totalMonths) || isNaN(usedMonths)) {
alert("Please enter valid numbers in all fields.");
resultDiv.style.display = "none";
return;
}
if (price < 0 || totalMonths <= 0 || usedMonths = totalMonths) {
// Warranty expired
customerPay = price;
credit = 0;
percentageUsed = 100;
message = "Your warranty period has expired. You must pay the full price for a replacement.";
} else {
// Calculate pro-rata
// Formula: Customer pays for the months used divided by total months
percentageUsed = (usedMonths / totalMonths);
customerPay = price * percentageUsed;
credit = price – customerPay;
// Convert to percentage for display
percentageUsed = percentageUsed * 100;
message = "Your warranty is valid. You receive a credit for the unused portion of the warranty.";
}
// Display Results
resultDiv.style.display = "block";
usageDisplay.innerHTML = percentageUsed.toFixed(1) + "%";
creditDisplay.innerHTML = "$" + credit.toFixed(2);
costDisplay.innerHTML = "$" + customerPay.toFixed(2);
statusMsg.innerHTML = message;
}
How to Calculate Pro Rata Warranty on a Car Battery
Understanding how a car battery warranty works can save you significant money when your vehicle fails to start. While some batteries come with a "Free Replacement" period, most extended warranties operate on a pro-rata basis. This calculator helps you estimate exactly how much credit you will receive and how much you will have to pay out of pocket for a new battery.
What is a Pro-Rata Warranty?
A pro-rata warranty is a partial warranty that covers the battery based on the amount of time it was used versus its total expected lifespan. Unlike a free replacement warranty, where you get a new battery at no cost, a pro-rata warranty acts as a discount on your next battery purchase.
Essentially, you pay for the "life" of the battery you used, and the manufacturer credits you for the "life" that was promised but not delivered.
The General Rule: The older your battery is, the less credit you receive towards a replacement. If the battery outlasts the warranty period (e.g., it dies in month 61 of a 60-month warranty), you receive no credit.
The Pro-Rata Calculation Formula
Most manufacturers use a straightforward linear formula to determine the cost. To calculate it manually, you need three numbers:
- Current Price: The current retail price of the replacement battery (not necessarily what you originally paid).
- Total Warranty: The length of the warranty in months (e.g., 60, 72, 84 months).
- Months in Service: How many months have passed since you bought the battery.
The Formula:
Customer Cost = (Months Used ÷ Total Warranty Months) × Current Price
Conversely, to find your credit amount:
Credit Amount = Current Price – Customer Cost
Real-World Example
Let's say you bought a premium battery with an 84-month warranty. It fails after 42 months. The current price of that battery at the store is $200.
- Calculate Usage Percentage: 42 months used ÷ 84 months total = 0.50 (or 50%).
- Calculate Your Cost: $200 price × 50% usage = $100.
- Result: You pay $100 for the new battery, and the warranty covers the other $100.
Important Considerations
- Free Replacement Period: Many warranties have a "Free Replacement" period (e.g., first 24 months) followed by a pro-rata period. If your battery dies during the free period, this calculator does not apply—you simply get a new one for free.
- Receipts are Vital: You almost always need your original receipt to prove the date of purchase. Without it, the manufacturer may use the manufacturing date code stamped on the battery, which could be months older than when you actually bought it.
- Testing Required: The retailer will usually require a load test to confirm the battery is actually defective and not just discharged due to a left-on light or alternator issue.